The present invention relates to a single-substrate-processing apparatus in a semiconductor processing system, and, particularly, to an improvement in a shower head used in the single-substrate-processing apparatus. The term "semiconductor processing" used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
There are CVD (Chemical Vapor Deposition) methods known as semiconductor processing methods of forming a film on a target substrate. Single-substrate-processing CVD apparatuses for processing semiconductor wafers one by one include a single-side-heating type of heating each wafer from the bottom side, and a double-side-heating type of heating each wafer from both the top and bottom sides.
Generally, a CVD apparatus of the single-side-heating type has a resistance heating body incorporated within a worktable, for heating a wafer only from the bottom side. Accordingly, there is a certain space above the wafer, large enough to arrange therein a shower head having a thickness of about 60 mm for supplying a process gas. The shower head has a void space in which a plurality of horizontal distribution plates are arranged, for uniformly distributing the process gas. A gas supply pipe is connected to the top of the shower head to communicate with the void space. There are a number of gas supply holes formed on the bottom of the shower head. The process gas is uniformly distributed in the void space by the horizontal distribution plates while it flows from the gas supply pipe to the gas supply holes.
On the other hand, a conventional CVD apparatus of the double-side-heating type has a structure as shown in FIG. 6. The apparatus is provided with a resistance heating body 11 arranged in a worktable 10 and heating means 12 arranged above the worktable 10 to face a wafer W. The wafer W is heated from both the top and bottom sides by the resistance heating body 11 and the heating means 12. Two gas supply pipes 13 and 14 are arranged to penetrate the left and right side walls of a process chamber and to have openings between the worktable 10 and the heating means 12. A process gas is supplied through the gas supply pipes 13 and 14, while the wafer W is heated from the top and bottom sides and the process chamber is exhausted through an exhaust pipe 15, so that a predetermined thin film is formed on the wafer W.
Sine the CVD apparatus of the double-side-heating type has the heating means 12 above the wafer W, it is difficult to use a shower head for the process gas, such as one used in the CVD apparatus of the single-side-heating type, in light of limits in space and in heat transmission. For this reason, as shown in FIG. 6, the process gas is supplied through the gas supply pipes 13 and 14 arranged at two positions above the peripheral portion of the wafer W. However, there is no means for uniformly distributing the process, and thus the process gas is apt to be supplied from the gas supply pipes 13 and 14 to the wafer W less uniformly.
Besides, the process gas is supplied in the process chamber at room temperature and hinders the surface of the wafer W in being heated by the heating means 12. Where the process gas is less uniformly distributed, so is a degree of hindering the heating of the wafer W, thereby lowering planar uniformity of the temperature of the wafer. As a result, a film formation process performed by the apparatus shown in FIG. 6 ends up as a less uniform process.
In order to solve this problem, there are ideas such that the gas supply pipes 13 and 14 are alternately caused to supply the process gas, and/or the wafer W is rotated during the process, so that the process gas is uniformly distributed. However, these ideas cannot increase uniformity in distribution of the gas so much. Further, these ideas require the gas supply pipes 13 and 14 to be provided with control valves for controlling their opening/closing, and/or the worktable to be provided with a rotating mechanism for rotating the wafer W, thereby making the apparatus complicated.